In a hostile environment, many bacteria will enter into a viable but nonculturable (VBNC) state. This state is a dormant form of non-sporulating bacteria, and may improve the survival of bacteria in a hostile environment. Currently, over 60 species of bacteria are known to be capable of entering into the VBNC state, most of which are pathogenic bacteria. The bacteria in the VBNC state still have metabolic activities, while cannot grow or form bacterial colonies on non-selective media commonly used for the bacteria. Therefore, conventional methods for bacteria detection, such as plate counting method, cannot detect the presence of bacteria in the VBNC state. As such, it is probably to underestimate the number of bacteria in a sample detected, bringing potential security risks to people. Therefore, conducting researches on the characteristic and formation mechanism of the bacteria in VBNC state is vitally important for effectively killing them. However, it takes a long time to obtain the bacteria in VBNC state, which thus limits the study progress thereof.
At present, the methods for inducing bacteria to enter into a viable but nonculturable state are primarily the method of oligotrophy combined with low temperatures. However, this method needs a long time for inducing, typically more than one month, thereby restricting the research progress of the bacteria in the VBNC state.